It is known that plastified and rigid polyester resin compositions are modified via addition of various additives, in order to obtain desired property profiles in the film webs or films produced therefrom. Known polyester resin compositions can be thermoformed and are suitable for a wide variety of applications, for example as packaging films, shrink films, and rigid films. Materials added for modification of these polyesters comprise modifiers to improve tensile impact strength, and to improve heat resistance, processing aids to improve processability and to improve the output of the production plant, lubricants to improve gelling performance during manufacture, flow aids to improve thermoformability and orientability, matting agents to reduce gloss, and the like. The proportions by weight of the individual additives are, as a function of requirements, from 0.1 to greater than or equal to 40% by weight. Preferred additives used comprise copolymers of the main polymer, but these are generally very expensive, and have to be used at high concentrations, and also often fail to bring about the desired extent of improvements in property profiles.
EP 1 066 339 B1 describes a process for production of a film or of a sheet composed of a polyester resin composition via calendering. The polyester component of the resin is an amorphous or semicrystalline polyester, whose crystallization half time from a melt is at least 5 min. The polyester component is composed of at least 80 mol % of a diacid radical component, of from 80 to 100 mol % of a diol radical component, and from 0 to 20 mol % of a modified diol. The diacid radical component is based on 100 mol % of diacid radical, and the diol radical is based on 100 mol % of diol radical. The resin composition includes additives which can, for example, be an internal lubricant, antislip agent, or a mixture thereof, or matting agents. The amount of each additive added is from 0.01 to 10% by weight, based on the total weight of the resin composition.
Surprisingly, amorphous or semicrystalline polyester resin compositions of this type are suitable for calendering with the aid of conventional calendering processes for production of films or sheets. Such polyester resin compositions are marketed by Eastman Chemical Co., Tennessee, USA, with the trademark CADENCE ®. The polyester compositions are usually used as main polymer for production of polyester films, their amount used generally being more than 96% by weight, based on the total weight of the polyester films.
EP 0 655 320 B1 discloses a corrugated film composed of at least 50% by weight of PET and from 10 to 45% by weight of fillers, and also from 5 to 20% by weight of rubber, the film having a crystallinity gradient across its thickness. The fillers are mineral fillers, selected from the group consisting of quartz, calcium carbonate, talc, titanium dioxide, glass fibers, and mixtures thereof. The film is especially used for construction purposes.
DE 102 56 493 A1 relates to a thermally activatable coating composition, which is sealable with respect to all types of paper, with respect to plastics, and with respect to metals, and also with respect to itself. The coating composition is based on an ethylene-acrylate polymer or on an ethylene-methacrylate polymer, if appropriate modified with polyester or polyamide, where the proportion of the main polymer is from 40 to 96.5%. The composition can moreover comprise polyvinyl chloride and/or polyvinyl acetate, and/or polyurethane dispersions.
DE 100 58 188 A1 discloses molding materials composed of an elastomeric polymer A and of at least one thermoplastic polymer B. The thermoplastic polymer B has been selected from vinylaromatic polymers, polymers based on methyl methacrylate, polyesters, polymers based on imides, or a mixture of these. The rubber-containing thermoplastic molding material is an acrylonitrile-butadiene-styrene polymer (ABS), an acrylonitrile-styrene-acrylate polymer (ASA), a methyl methacrylate-acrylonitrile-butadiene-styrene polymer (MABS), or an acrylonitrile-(ethylene-propylene)-styrene polymer (AES). Moldings, films, fibers, and foams are produced from the molding material, the moldings being injection moldings.
Additives suitable for use in the inventive films are generally used in calendering of polymers, such as PVC or polyester.
EP 1 066 339 B1 discloses by way of example addition of antislip agent or lubricant as additive to the polyester resin composition, the selected proportion of these additives being from 0.01 to 10% by weight, based on the total weight of the polyester resin composition. The polyester resin compositions can moreover comprise an oxidative stabilizer and a melt-strength improver.